Cannot reach A/C high/low pressures

This is a 1990 Geo Metro. This car was previously converted to R134a.
Recently I replaced the compressor and dryer. I did everything by the
book. I flushed the system with isopropyl alcohol, replaced o-rings,
evacuated, oiled it and held a vacuum for several hours. There were no
leaks. I even purged it again with dry N2 and evacuated again.

Book calls for 1.1 lb of refrigirent (this was for R-12, so I was ready
to use only 1 lb of R134a). After putting in 1 lb of R134a, the
pressure did not reach the specified values (200/25 psi on the high/low
sides). I added some extra refrigirent, and then some more. The
pressure was still low. I ended up putting in twice the required amount
of refrigirent. But the pressure was still only 125/25 psi. I do not
hear or see any obvious signs leaks. Even if there were a leak,
wouldn't the pressure initially go up and then slowly come down? Where
is all the extra refrigerent going? The air is blowing a little cool,
but nowhere near where it should be. The high side tubes are hot, which
is a good sign. The compressor is turning over fine, and there are not
funny sounds. I am at a loss what to try next.

Any suggestions are appreciated.